Sir, For years plastic carrier bags were ignored. Their existence passed without comment they were as ubiquitous as they were innocuous, or so we thought. Little did we know that we were sitting on an environmental time bomb (‘Why those free plastic bags are stil hanging on in there’, 06 August).

In truth, this environmental enemy number one the so-called ‘single use carrier bag’ is nothing of the sort. However, no matter how much pro-bag evidence is produced, the anti-bag lobby remains unmoved.

So here are a few hard facts that have conveniently been omitted from the debate. Newly published government research shows that a thin supermarket carrier bag is 171 times less damaging to the environment than a cotton bag and produces less then one third of the CO2 emissions of a paper bag.

In the Republic of Ireland, which has introduced a bag levy, the consumption of supermarket carriers has been cut, but the sale of bin liners and nappy sacks has jumped by a massive 80%.

And here’s the clincher in Hong Kong, which has had a bag tax for two years, the amount of plastic used in bags has increased by more than 25%.

There is clearly a debate to be had about plastics and the environment but until the facts are included in the discussion it’s going to be a wholly pointless one.

Anthony Clark, news editor, PRW